Legend in python without labels

Question

I would like to show a fixed legend in a python matplotlib plot. I am creating a large set of plots, and some of them lack one of the datasets I am using. Let's say I have

data1, plotted in green

data2, plotted in blue

data3, plotted in blue

for some cases, dataX is missing, but I would like to show the whole legend (always the three colours). All I have found so far is based on labeling the data you plot, so: is there anyway to create a legend independent of the data you are plotting, and specify the symbol and colors when creating the legend?

Thanks!

Answer 1

For the plots where dataX is missing, you can call the plot command as normal, just leave the x and y arrays empty:

import matplotlib.pyplot as plt

plt.plot([0.1,0.5], [0.1,0.5], color='g', label='data1')
plt.plot([], [], color='b', label='data2')
plt.plot([0.2,0.6], [0.1,0.5], color='b', label='data3')
plt.legend(loc=0)